The present invention relates to a welding machine of which welding tool, such as a welding torch, is moved by automated equipment such as a robot. More particularly, it relates to a welding machine manipulated by the automated equipment and performing arc welding using a consumable electrode.
In arc welding, it is important to move a welding torch maintaining a relative position between a work-piece and the welding torch. Welding by a robot has an advantage of higher speed over welding by holding a torch with a worker""s hand (hereinafter referred to as xe2x80x9cmanual weldingxe2x80x9d). Reproducibility in repeating operations is also important in welding. Regarding high-speed-welding in particular, which allows little tolerance for disperse of relative positional relation between the work-piece and the welding torch, the manual welding cannot deal with it but a robot welding can do it. As a result, welding machines manipulated by automated equipment expand their application extensively.
A case of gas shielded metal arc welding, which uses a dc power source having a constant voltage characteristic as a welding power source, and also uses a consumable electrode as a welding electrode, is described hereinafter.
A voltage at an electrode is dependent both on an arc voltage and a weld-electrode-resistance, so that an amount of heat given to the welding electrode is controlled by a welding current. Heat generated melts metal, so that supply quantity of depositing metal is determined with respect to the current. In other words, when an arc voltage and a wire extension remain constant, the welding current is determined by a supply quantity of the depositing metal (=welding wire). A voltage supplied to the electrode is referred to as a welding voltage. This welding voltage and the welding current are controlled by a welding controller. The welding manipulated by automated equipment such as a robot has been controlled basically in the same way as the manual welding.
If the heat amount generated is constantly used for melting the depositing metal, uniform welding is always expected. However, there are the following abnormal cases: a work-piece has a gap and the gap is uneven, or a thickness of the material constituting the work-piece varies depending on spots, or a member of greater heat capacity is disposed near a groove and thus the heat is absorbed unevenly. For these cases, an amount of depositing metal supplied should be finely controlled responsive to the heat amount generated depending on spots along a weld line.
FIG. 3 shows a depositing metal feeder. In FIG. 3, welding wire 12 wound on spool 11 is pulled out, then fed to a welding torch (not shown) by wire feeder 14 driven by motor 13. Motor 13 is powered through cable 15, which also couples motor 13 to a controller (not shown). Cable 15 transmits a control signal, e.g., an armature voltage signal in addition to powering motor 13. Spool 11 is held by base 17, and wire feeder 14 as well as driving motor 13 is held by base 18.
FIG. 6 shows a control system of a conventional depositing metal feeder. Depositing metal feeder 21, detailed in FIG. 3, is controlled its feeding of the depositing metal by feeder controller 22 via cable 15. Feeder controller 22 follows a signal transmitted via cable 25 from welding controller 24 built in welding power source 23, and controls feeder 21. In other words, feeder 21 is controlled by welding controller 24 built in power source 23. Welding wire 12 is fed to the welding torch (not shown) to be welded. Power cable 16 supplies a welding current and a welding voltage from welding power source 23 to the welding torch. In general, power cable 16 transits wire feeder 14 and is led to the torch by a torch cable (not shown). Welding power source 23 is powered from outside via input cable 26.
As discussed above, in the conventional control system of the depositing metal, welding power source 23 powers the torch, while welding controller 24 built in power source 23 controls the wire feeding. Therefore, fine control, such as varying the supplying amount of the depositing metal responsive to the heat amount generated depending on spots along the weld line, could not be expected.
A welding machine is manipulated by automated equipment, where the automated equipment can control a supplying amount of depositing metal while a welding controller controls a welding current and a welding voltage during the welding. A welding machine in an exemplary embodiment of the present invention comprises the following elements:
(a) automated equipment for moving a welding tool relative to a work-piece;
(b) an equipment controller for controlling the automated equipment;
(c) a depositing metal feeder for feeding the depositing metal to a weld point nearby the welding tool; and
(d) a depositing metal feeder controller for controlling the depositing metal feeder.
In the construction discussed above, the equipment controller is coupled to the feeder controller so that a signal related to feeding the depositing metal is transmitted from the equipment controller to the feeder controller.
This structure allows a feeding amount of the depositing metal to be controlled by the information of a fed amount of the depositing metal on the equipment controller side in addition to the information about a welding current and a welding voltage supplied from a welding controller on a welding power source side. Therefore, an optimum welding condition for respective weld points along a weld line is obtainable. As a result, quality welding can be achieved.